Patent GB-821646-A (GB)
Title: Method and apparatus for bending glass sheets
IPC: C03B23/027
Filed: 1956-08-07
Abstract: 821,646. Glass shaping moulds. LIBBEYOWENS-FORD GLASS CO. Aug. 7, 1956 [Aug. 11, 1955], No. 24120/56. Class 56. In bending a glass sheet about both major axes, the sheet is supported on a mould with a skeleton type shaping surface and moved through a bending furnace where radiant heat is directed at the glass to raise it to bending temperature, the heating of the glass being retarded in a spaced position extending inwardly a limited distance from a side edge and spaced inwardly from opposed end edges thereof and, when the other sheet portions are at bending temperature, the sheet is lowered or allowed to sag with contact with the mould shaping surface. Glass sheets 61, 62, Fig. 3, are to be bent steeply at each side and also almost to a right angle at c, along the line y-y, to form a windscreen 25 with a main, slightly curved section b extending across the car and the bent back sides joining the sides of the car at f and a top part a to be joined to the roof, the side edges being cut away at 26. The ends are first bent up and the whole curved transversely on a mould 29 Fig. 7, comprising a centre section 34 and end sections 35 hinged thereto, the glass sheets being supported on the end rail section 48 of the sections 35 in the opened out position and on support blocks 63 arranged to move downwardly to below the shaping surfaces 42 of the centre section 34 as the end sections 35 move upwardly to shape the glass. At the same time, a slight curvature on the line y-y is given to the glass sheet as shown in dot-dash lines on Fig. 15. The parts of the sheet to be curved only slightly are protected from the radiant heat from below by shields 73, 74 extending as shown over the main part of the shaping surfaces 42 and to within an equal distance of the line y-y. The shields are of material of higher specific heat than glass and act also to withdraw heat from these parts. The glass sheets are then cooled so that they retain their bent shape, and cut out at 26 to leave apices g, h, the sheets then being placed on a second mould 93, Figs. 12, 13, having a fixed shaping rail 98. The shaping rail front or top portion 99 has a wider surface than the rear or lower edge rail portion 100 to allow movement thereover of the glass sheets, the rail surface 99 being at a slight angle to the horizontal in its centre portion and becoming nearly vertical at the apices h, g, the angle reversing either side of the apex h to allow the glass to slide thereover evenly. The narrow rail surface 100 is similarly angled, rising to nearly vertical at apex g. Shields 140, 141 below the mould 93 are placed similarly to the shields 73, 74 for the same purposes and shields 128, 129 are provided above the same areas to protect from radiant heat only, the gap 132 between them being smaller than the gap 142 between the lower shields 140, 141. The shields 128, 129 are mounted on cross bars 135 having dowels 138 to engage removably in the tops of hollow rods 136 mounted in the mould frame 92. To exert downward pressure on the sharply curved ends of the glass sheets, a movable press member 109 is removably mounted by a cross rod 116 in slots 126 in blocks 124, where it is held by pins 127. The rail 110 corresponds to and may engage the ends of the rail 98, but is normally held out of position by a notch 121 on a bar 118 pivoted thereto engaging a groove in a lock bar 122. On passing through the bending furnace, the ends of the glass sheets and the area adjacent the bending line y-y are brought to softening point and the sheets sag onto the mould 93, the edges of the sheets sliding down the broad rail surfaces 99. The bar 118 is then manually disengaged and the press member 107 lowered to bear against the ends of the sheet to press then to the required shape. After annealing, the sheets are slowly cooled and cut to final shape. A third mould may then be used, to relieve strains produced in the glass, the mould having hinged ends, with limited movement only, to allow for slight variations of curvature and having lower protective shields . only. The mould is passed through a furnace to remove strain patterns and is subjected to temperatures somewhat less than normal bending temperatures so that the sheets will conform to the shaping rail of the mould but will not sag. After annealing the sheets may be laminated with a plastic interlayer. Specifications 727,200 and 745,992 are referred to.